aligning equations in latex

Question

Hi all,

I have the following code in an attempt to align things in latex using amsmath package:

\begin{alignat}{3}
\text{max}  && c^Tx &=\\
\text{s.t.} && Ax &\leq  b \\
     && x  &\geq  0
\end{alignat}

Basically, i would like for max and s.t. to be in one column, c^Tx, Ax, x to be in second column, and lastly b and 0 to be in the last column. I'm not sure why it doesn't work (it clumps max and c^Tx together for some reason.

if anyone can help me out with this it would be much appreciated!

Answer 1

With math-mode \text{} you should put in some explicit whitespace such as \quad. But max smells like a log-like symbol so you should be using pre-defined \max or self-defined \operatorname{max} instead of \text{max}.

Additionally, the parameter for the alignat environment should be 2 in this case. The param is the number of alignment structures and can be calculated by solving n from a=2n-1 where a is the number of ampersands on a row. However, it doesn't seem to have a difference in this case.

Answer 2

I believe what's happening here is that max and s.t. are being right-aligned, which is running them right up next to c^Tx and Ax. If you just add some whitespace to the right-hand-side of max and s.t., you should be in business.

(Also, laalto is right, you should definitely use \operatorname{max} if max is some sort of operator or function. Though I'm not really sure what you're doing, so maybe it isn't.)